Miniature delay line

ABSTRACT

A delay line for use at high frequencies. The delay line has a core having a core member with at least one pair of flanges therein. A silver paint layer covers the plastic core, and a multiturn coil of a resin-coated wire is wound on the core between the flanges. Terminals are provided on the core appropriately connected to the wire of the coil and to the silver paint layer, and the core and coil are enclosed in a housing.

- United States Patent 1 Tamura et a1. a

[i 3,750,054 July 31, 1973 1 MINIATURE DELAY LINE "[75] lnventors: Toru Tamura; Shigeru Kondo; Kozo I-lashimoto, all of Osaka, Japan [73] Assignee: Matsushita Electric Industrial Co.,,

Ltd., Osaka, Japan [22] Filed: Oct. 26, 1971 [21] Appl. No.: 192,224

[30] Foreign Application Priority Data Mar. 24, 1971 Japan 46/17418 Mar. 24, 1971 Japan 46/17419 Mar. 31, 1971 Japan 46/19917 Mar. 3, 1971 Japan 46/13719 [52] US. Cl... 333/29, 333/31, 29/60, 336/198 [51] Int. Cl l-l03h [58] Field of Search 333/29, 31, 31 C; 336/198, 205, 212, 219; 29/600 [56] I References Cited UNITED STATES PATENTS 3,675,174 7/1972 Horbach. 336/198 3,617,949 11/1971 Kameya et al. 333/29 2,810,887 10/1957 Ecklund et 81.... 333/198 2,823,354 2/1958 Lubkin 333/29 3,063,136 11/1962 Cammauf 336/205 X 3,308,414 3/1967 Ostrander et al. 336/205 10/1967 Foerster 336/205 X Primary Examiner-Rudolph V. Rolinec Assistant EXamirrer-Saxfield Chatmon, Jr. g Ai IoFh eY- E FQ Wender oth, V. M. Creedon et a1.

[5 7] ABSTRACT A delay line for use at high frequencies. The delay line has a core having a core member with at least one pair of flanges therein. A silver paint layer covers the plastic core, and a multiturn coil of a resin-coated wire is wound on the core between the flanges. Terminals are provided on the core appropriately connected to the wire of the coil and to the silver paint layer, and the core and coil are enclosed in a housing.

9 Claims, 6 Drawing Figures.

PAIENTED JUL3 1 ma SHEEI 1 (If 3 SHIGERU KONDO and. K020 HASHIMOTO,

IN VENTOR S BY #Zmk ATTORNEY$ PAIENIEU .750.054 sum 2 or 3 TORU TAMURA, SHIGERU KONDO and K020 HASHIMOTO INVENTORS ATTORNEYS PATENIEDJUL31 ma sum 30F a L 4 I. m I O 6 9 I m X w m T w A y 0 v W m w w E a m C E w all wUZ .:U & .wO U365 mTC. d H E T m x C O I Q M X E W VT 0 w T T CAPACITANCE vs. TEMP.

TEMPERATURE (C) TORU 'IAMURA, I SHIGERU KONDO and K020 HASHIMOTO INVENTOR ATTORNEYS MINIATURE DELAY LINE This invention relates to a miniature delay line, having distributed constants for use with high frequency signals, and more particularly to a delay line having a plurality of coils wound on a plastic core which has a conductive silver paint thereon.

Miniaturization of electronic equipment for use in high frequency equipmengsuch as color TV sets, has required increasingly smaller components such as miniaturized delay lines. A delay line for use at a high frequency such as MHz heretofore has had acoil delay line of the distributed constants type comprised of a thin wire and a thick wire wound on a core. Such a conventional coil delay line requires large dimensions, for example, a mm diameter and a 145 mm length in order to provide the necessary capacitance. Another type of delay line is a combination of two discrete components of capacitance and inductance. This type of delay line can be miniaturized to a size, for example 12X 1 2X45 mm, but the frequency at which it can operate is limited, for example, to about 218 Ml-Iz. It is rather difficult for this type delay line to maintain a low eddy current loss at high frequency. Therefore, there is a great requirement for a miniaturized delay line for use at a high frequency, such as 5 MI-Iz.

An object of the present invention is to provide a miniature delay line for use at a high frequency, yet which has small power loss. I

Another object of the invention is to provide a miniature delay line characterized by a small temperature dependence of capacitance-A further object of the present invention. is to provide a miniature delay line characterized by a small temperature dependence of 1 capacitance. I v

A further object of the present invention is to provide a method for making a miniature delay line which is operable at high frequency and which has a small temperature dependence of capacitance and a small power loss.

The delay line according to the present invention comprises a plastic core having at least one pair of plastic flanges, the core and flanges being a unitary body, said unitary body being coatedv with a layer of silver paint, a multiturn coil of a resin-coated wire wound on said core, a coil filler filling said multiturn coil, a terminal mounted on one end of said plastic core, and which is insulated from said silver paint layer and being conductively connected to one end of said wire, two terminals mounted on another end of said plastic core, one

of said two terminals being conductively connected to said silver paint layer and the other of said two terminals being insulated from said silver paint layer and being conductively connected to the other end of said wire, and a housing enveloping said plastic core and said multiturn coil.

The invention will be better understood from the following description taken together with the accompanying drawing, wherein:

FIG. 1 is a perspective view of a miniature delay line according to the present invention;

FIG. 2 is a sectional view along a section line through the terminals 17 and 18 of FIG. 1;

FIG. 3 is a sectional view of the wire for use in a coil;

FIG. 4 is a perspective view of a delay line enveloped in a housing in accordance with the present invention;

FIG. 5 is a: circuit diagram of an equivalent circuit of a delay line according to the present invention; and

FIG. 6 is a graph illustrating the temperature dependence of one embodiment of a delay line according to the present invention.

A delay line according to the present invention, as shown in FIGS. 1, 2'and 4, has a plastic core comprised of a core member 16 and at least one pair of plastic flanges integrally formed therewith. In the embodiment of these figures, the core has flanges 1-15. The unitary core composed of the core member 16 and flanges l-1 5 is coated with a layer of silver paint 20. A multiturn coil 22 of a resin coated wire. 23 is wound on said core with a section between each pair of flanges, i.e. between flanges l and 2, between flanges 2 and 3, etc.,

' and each section is filled with a coil filler 21 for adjusting the capacitance thereof. A terminal 17 is mounted v on one end of said plastic core, e.g. on flange l, and is insulated from said silver paint layer 20. Tow termianls l8 and 19 are mounted on the other end of said plastic core, e.g. on flange 15. The terminal 19 is conductively connected to said silver paint layer 20 and the other terminal 18 is insulated from said silver paint layer 20.

The opposite ends of multiturn coil 22 are connected to the two insulated terminals 17 and 18, respectively. Said plastic core with said multiturn coil 22 thereon is enveloped in a housing 25 in a way such that said multiturn coil 22 is spaced from the interior surface of the housing wall.

Referring to FIG. 3, said resin coated wire 22 is composed of a conductive metal wire 23 coated with a resin layer 24. A preferred resin for said resin layer 24 is one selected from the group consisting of polyurethane, polyamide polyethylene, polyester, polyvinylformal, and combinations thereof. Said resin layer 24 acts as a dielectric layer and the thickness is made such as will produce the desired capacitance. A smald thickness results in a high' capacitance, but is apt to produce more pin holes which increase the leakage current. For a satisfactory capacitance and leakage current, a preferred thickness is, 10 to 20 microns.

It is rather difficult to. provide a satisfactory capacitance only by means of said resin layer 24. A satisfactory capacitance is obtained by filling the sections of range of -40 to C in addition to helping provide a satisfactory capacitance. I

The plastic core member 16 with'at least one pair of plastic flanges can be made of any available and suitable plastic. A delay line which is very stable with respect to temperature can be made by using plastic which has a thermal expansion rate less than 10' over a temperature range'of Oand C. A preferred plastic is one selected from the group consisting of phenolic resin, epoxy resin, and polyester resin.

The silver paint layer 20 acts as an electrode for a capacitor composed of the resin layer 24 and the coil filler 21. The other electrode for said capacitor is the conductive metal wire 23. The delay line according to the present invention forms, between two adjacent flanges, a plurality of capacitors, the number corresponding to the number of turns in said coil 22, as indicated by the equivalent circuit of FIG. 5. The inductance L of FIG. 5 is produced by the coil 22. The mere use of the coil 22 is apt to produce a high eddy current loss when the delay line is used at a high frequency such as 5 MHz. It has been discovered according to the present invention that the use of the silver paint layer 20 reduces the high eddy current loss. The use of a layer formed by electroless plating of a metal such as copper or nickel instead of a silver paint layer does not satisfactorily reduce the high eddy current losses. To satisfactorily limit eddy current losses and produce satisfctory action as an electrode of the capacitor, the silver paint layer 20 should preferably have a specific surface electric resistivity of l to ohms. The thickness of the silver paint layer 20 has an effecton the eddy current loss, and is preferably 10 to 100 microns.

One method for making the delay line comprises the following steps, in combination: forming a plastic unitary core having a core member and at least a pair of flanges; treating the surface of said plastic unitary core I with a trialkyl benzylammoniumchloride type surface active agent, such as polyvinylbenzyl trimethylammonium chloride; drying the treated plastic unitary core; dipping the dried plastic unitary core into a silver paint; curing said silver paint; providing a multiturn coil on said core; filling said multiturn coil with a coil filler; mounting one terminal at one end of said unitary core and two terminals at the other end of said unitary core; and housing the resulting unitary core.

The silver paint referred to herein is paint having silver particles dispersed in a resin bonding vehicle and is electrically conductive when it has been cured. However, the silver paint is not the only type of paint which can be used. A satisfactory result can be obtained with conductive paint which has copper particles, nickel particles, gold particles or combinations thereof dispersed in a resin bonding vehicle and which has a function similar to that of the silver paint layer when it has been cured.

A specific embodiment of this invention will be described with reference to FIGS. 1 4, but should not be construed as limitative.

Phenolic resinisformed into a unitary core having a core member 1 and flanges by any well-known plastic forming technique. Said core member 16 is 5 mm in diameter and 45.1 mm in length. Said l5 flanges are spaced 0.7 mm from each other and are almost square, having dimensions of 9.5 9.0 2.35 mm. Said unitary core has the surface treated with a surface active agent of the trialkyl benzyelammonium chloride type and is then dried at 50C for 1 hour. The dried unitary core is dipped into a silver paint commercially available under the trade name of Dotite D-775 from Fujikura Kasei Co., Ltd. in Japan. The silver paint adhered to the surface of said unitary core is cured at 100C for 1 hour. The thus produced layer of silver paint has a specific surface electric resistivity of 4 ohms and a thickness of 100 microns. Each space between two adjacent flanges is provided with a coil section having 100 turns, except for the two end spaces, each of which is provided with a coil section having 115 turns.

Said coil sections each comprise a copper wire having a diameter of 80 microns and having a polyurethane coating layer 20 microns thick thereon. The unitary 120C for 10 seconds in order to fill the coil sections with polymethyl phenyl silicone. One terminal is mounted on one end of the resultant unitary core in a way such that it is insulated from the silver paint layer. Two terminals are mounted on the other end. One of said two terminals is insulated from said silver paint layer. The insulation is achieved by rubbing a small area of silver paint off.

The final unitary core having the three terminals mounted thereon is inserted into a housing of phenol resin and fitted with dry air and is covered with an elastic lid of porous polyurethane resin. Fluid epoxy resin is poured 'on the lid, which acts as'a protector against penetration of the fluid epoxy resin into the housing. After curing of the epoxy resin at room temperature, the housing is tightly sealed. Any penetration of the epoxy resin causes a greater variation in the capacitance of the resultant dely line with temperature, and should be avoided.

The thus produced delay line has the following specifications:

Characteristic impedance 1800 ohms Time delay 1.15 microseconds Nominal frequency range 5 megacycles Capacitance 650 P.F. Inductance 2.05 milihenries As shown by the solid line of FIG. 6, the thus produced delay line has a very small variation in the capacitance with temperature. A like delay line having no coil filler has a lower capacitance and has a larger variation in the capacitance with temperature, as shown by the dotted curve of FIG. ,6.

What is claimed is:

1. A delay line comprising a core having a plastic core member having at least one pair of plastic flanges integrally formed therewith, a silver paint layer on said unitary core, a multiturn coil of a resin-coated wire wound on said core between said flanges, a coil filler filling said multiturn coil, a terminal mounted on one end of said plastic core and being insulated from said silver paint layer and being conductively connected to one end of said multiturn coil, two terminals mounted on the other end of said plastic core, one of said two terminals being conductively connected to said silver paint layer and the other of said two terminals being insulated from said silver paint layer and being conductively connected to the other end of said wire, and a housing enveloping said plastic core and said multiturn coil.

2. A delay line according to claim 1 wherein said multiturn coil is spaced from the interior surface of the housing.

3. A delay line according to claim 1 wherein said silver paint layer has a specific surface electric resistivity of l to 10 ohms.

4. A delay line according to claim 3 wherein said silver paint layer has a thickness of 10 to microns.

5. A delay line according to claim 1 wherein said coil filler is a material selected from the group consisting of polymethyl pehnyl silicone, polyalkylphenyl silicone, polydimethyl silicone, poly-trifluorochloroethane and combinations thereof.

6. A delay line according to claim 1 wherein said resin-coated wire is coated with a resin selected from the group consisting of polyurethane, polyamide and combinations thereof, and has a thickness of 10 to 20 microns.

7. A delay line according to claim 1 wherein said unitary core is a plastic selected from the group consisting of phenolic resin, epoxy resin and polyester resin.

8. A method for making a delay line comprising the curing said silver paint, providing a multiturn coil on said core between said flanges, filling said multiturn coil with a coil filler, mounting one terminal on one end of said unitary core, and two terminals on the other end of said unitary core, and enveloping the resulting unitary core in a housing.

. '9. A method for making a delay line according to claim 8 wherein said resulting unitary core is enveloped in a housing filled with dry air.

i i I I l 

2. A delay line according to claim 1 wherein said multiturn coil is spaced from the interior surface of the housing.
 3. A delay line according to claim 1 wherein said silver paint layer has a specific surface electric resistivity of 1 to 10 ohms.
 4. A delay line according to claim 3 wherein said silver paint layer has a thickness of 10 to 100 microns.
 5. A delay line according to claim 1 wherein said coil filler is a material selected from the group consisting of polymethyl pehnyl silicone, polyalkylphenyl silicone, polydimethyl silicone, poly-trifluorochloroethane and combinations thereof.
 6. A delay line according to claim 1 wherein said resin-coated wire is coated with a resin selected from the group consisting of polyurethane, polyamide and combinations thereof, and has a thickness of 10 to 20 microns.
 7. A delay line according to claim 1 wherein said unitary core is a plastic selected from the group consisting of phenolic resin, epoxy resin and polyester resin.
 8. A method for making a delay line comprising the steps of forming a plastic unitary core having a core member and at least one pair of flanges integral therewith, treating the surface of said plastic unitary core with a trialkyl benzylammonium chloride type surface active agent; drying the treated plastic unitary core, dipping the dried plastic unitary core in a silver paint, curing said silver paint, providing a multiturn coil on said core between said flanges, filling said multiturn coil with a coil filler, mounting one terminal on one end of said unitary core, and two terminals on the other end of said unitaRy core, and enveloping the resulting unitary core in a housing.
 9. A method for making a delay line according to claim 8 wherein said resulting unitary core is enveloped in a housing filled with dry air. 